1,721,086 research outputs found
Predicting the toxicity of substituted phenols to aquatic species and its changes in the stream and effluent waters
No full textThe changes in the acute toxicity of 16 phenols toward Selenastrum capricornutum and Daphnia magna were examined as a function of their physical/chemical properties. The results demonstrated that phenols with a higher octanol-water partition coefficient (K-ow) had a higher toxicity toward aquatic organisms. The toxicity of phenols was closely related to the log K-ow values, with correlation coefficients of 0.93 (except for the nitrophenols) and 0.89 for S. capricornutum and D. magna, respectively. The changes in the phenols toxicities in the site waters (i.e., stream and effluent waters) were investigated by calculating the water effect ratios (WER) from the results of the toxicity tests in the site waters using D. magna. The results showed that the degree of ionization for each phenolic compound was altered by the differences in the dissociation constant (pK(a)), and the change in the toxicity could be predicted. Therefore, the WER should be considered when the toxicity of phenolic compounds is estimated in site waters. The quantitative structure-activity relationships (QSAR) study showed that the toxicity of the phenols to D. magna could be predicted by the hydrophobicity (log K-ow) alone and by combining the log K-ow with pK(a), while the toxicity to S. capricornutum was predicted by a combination of hydrophobicity (log K-ow) and E-LUMO (or pK(a)).X1118sciescopu
Use of response surface analysis in selective bioconversion of starch wastewater to acetic acid using a mixed culture of anaerobes
No full textStarch-processing wastewater was treated to maximize acetic acid production using a mixed culture of acidogenic anaerobes, which were identified as Acetobacterium woodi, Centipede periodontii, Desulfobulbus elongatus, Lactobacillus rhamnosus, Lactobacillus casei, and Lactococcus plantarum. The maximum production of acetic acid associated with simultaneous changes in hydraulic retention time (HRT), pH, and temperature was investigated. The conversion efficiency of organics in the wastewater to acetic, propionic, and butyric acids ranged from 71.1 to 98.3%. The concentrations of estimated total organic carbons (TOCs) due to the formation of acetic acid ranged from 268 to 672 mg/l, which accounted for 29.7 and 72.2% of influent TOC concentration, respectively. Using a response surface methodology (RSM) with an orthogonal cube design. the maximum production of acetic acid was 1681 +/- 49 mg/l at 0.56 day HRT, pH 5.9 and 36.1 degreesC, which was 75.2% conversion efficiency. Systematic model-building along with statistical analysis using a RSM, could play an important roles in elucidating basic mechanisms in complex situations and thus providing better process control in maximizing acetic acid production with respect to the effects of HRT, pH, and temperature. (C) 2003 Elsevier Ltd. All rights reserved.X116sciescopu
A dual-band internal antenna with a parasitic patch for mobile handsets and the consideration of the handset case and battery
No full textThis letter proposes a compact internal antenna of the modified planar inverted F antenna (PIFA) type with a parasitic patch. It also considers the influences of the handset case and battery. A low-profile design is implemented on both the top and bottom sides of the FR-4 substrate. The proposed antenna, with the small size of 27.5 x 12 x 7 mm(3), can be easily placed in the actual handset. The measured bandwidths of the proposed antenna with handset case and battery (VSWR < 2) can cover 140 MHz (1740-1880 MHz) in the Korean personal communication service (KPCS) band and 90 MHz (2400-2490 MHz) in the Bluetooth band. Numerical simulation and experiment results of antenna electrical performance are investigated by considering the antenna, the phone case, and the battery
An advanced contrast enhancement using partially overlapped sub-block histogram equalization
No full textIEEE Transactions on Circuits and Systems For Video TechnologyIn this paper an advanced histogram-equalization algorithm for contrast enhancement is presented. Histogram equalization is the most popular algorithm for contrast enhancement due to its effectiveness and simplicity. It can be classified into two branches according to the transformation function used: global or local. Global histogram equalization is simple and fast, but its contrast-enhancement power is relatively low. Local histogram equalization, on the other hand, can enhance overall contrast more effectively, but the complexity of computation required is very high due to its fully overlapped sub-blocks. In this paper, a low-pass filter-type mask is used to get a nonoverlapped sub-block histogram-equalization function to produce the high contrast associated with local histogram equalization but with the simplicity of global histogram equalization. This mask also eliminates the blocking effect of nonoverlapped sub-block histogram-equalization. The low-pass filter-type mask is realized by partially overlapped sub-block histogram-equalization (POSHE). With the proposed method, since the sub-blocks are much less overlapped, the computation overhead is reduced by a factor of about 100 compared to that of local histogram equalization while still achieving high contrast. The proposed algorithm can be used for commercial purposes where high efficiency is required, such as camcorders, closed-circuit cameras, etc
Align-free assembling of connectors and modules on an optical PCB for chip-to-chip optical interconnection
No full textBiosorption of 1,2,3,4-tetrachlorodibenzo-P-dioxin and polychlorinated dibenzofurans by Bacillus pumilus
No full textMicrobial adsorption of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) and various polychlorinated dibenzofurans (PCDFs) was investigated in an effort to determine the significance of microorganisms as potential agents in transferring the molecules in the environment. The microorganisms used in this study were cultivated under low nutrient conditions for 2 months. The increase and decrease of 1,2,3,4-TCDD and PCDFs in the samples were measured by GC/MS. The peak of dibenzofuran (DBF), added as an internal standard, was compared with the peaks of 1,2,3,4-TCDD and PCDFs. The results showed that the dead biomass of microorganisms could remove these molecules from the medium more effectively than live cells. The subsequent studies suggested that the removal of the molecules be concerned with the unknown biocompound(s) of which secretion is pronounced at high temperature. UV-VIS spectrometry was used to monitor the change in the concentration of biocompound(s). (C) 1999 Elsevier Science Ltd. All rights reserved.X1117sciescopu
Biokinetic evaluation and modeling of continuous thiocyanate biodegradation by Klebsiella sp.
No full textBiokinetics for autotrophic degradation of thiocyanate using batch culture of Klebsiella sp. were evaluated both analytically and numerically. A sequential approach with an analytical method followed by a numerical approximation was used to evaluate and to ensure the accuracy of the parameter estimation. The nonlinear least-squares method with a 95% confidence interval was employed. The growth conditions were maintained at pH 7 and 38 degreesC for all experiments. With an automated incubation and turbidity reader, a total of 16 different initial thiocyanate concentrations, ranging from 10 to 300 mg L-1, were used to develop a kinetic expression of specific growth rate as a function of substrate concentration. The biodegradation of thiocyanate with Klebsiella sp. followed a substrate inhibition pattern. Three identical automated bioreactors with working volumes of 1.5 L, equipped with sterilizable sampling ports, were also used for the numerical approximation of the biokinetic parameters in batch mode. A fourth order Runge-Kutta method was used to approximate the substrate inhibition kinetics of the Klebsiella sp. utilizing thiocyanate. Although the kinetic coefficients estimated by analytical and numerical methods were not statistically different at a 0.05 alpha level, model responses of numerical approximation generated a better prediction of changes in thiocyanate and cell mass concentrations. The hypothetical maximum growth rate, mu(m) half saturation coefficient, K-s, microbial yield coefficient, Y, cell mass decay rate coefficient, k(d), and substrate inhibition coefficient, K-si, were evaluated as being 0.62 +/- 0.05 d(-1), 85 +/- 8 mg SCN- L-1, 0.076 +/- 0.011 mg cell mass (mg SCN)(-1), 0.03 +/- 0.002 d(-1), and 131 +/- 22 mg SCN- L-1, respectively. The calculated maximal substrate concentration, S-m and apparent maximum specific growth rate, mu'(m), were 105.5 +/- 8.7 mg SCN- L-1 and 0.24 +/- 0.01 d(-1), respectively. Using these estimated parameters, the theoretical performance of the continuous operation was also illustrated, which depicts the residual thiocyanate and Klebsiella sp. concentrations in the non-steady and steady states at different hydraulic retention times (HRTs). Assuming the influent concentration of 250 mg SCN- L-1, the expected treatment efficiency ranged from 94.9% to 69.4% between 20 and 5 days HRT, respectively. Klebsiella sp. was expected to be washed out at 4.8 days HRT, thus resulting in no treatment of thiocyanate.X111414sciescopu
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